I don't think so. Games like Age of Empires allowed you to use every tile in the game and I don't recall reading anyone saying it was bad in performance. I think DSG did explain some of the reasons behind it at some point. Still, I'm pretty sure the game can use more without going haywire.
I remember I found some bug in the Editor during the Beta that appeared it would allow more than 8 tiles, but I no longer have that particular map.
P.S. — But yeah, it was pretty mean of Blizzard to do that when they know people have been trying to break those limits for some time, both in RP and AWS-like maps. Fortunately, I believe that Decals can be used as a workaround.